mastra-ai/mastra · error · MastraError

WEB_SEARCH_UNSUPPORTED_PROVIDER

WEB_SEARCH_UNSUPPORTED_PROVIDER

Error message

The built-in webSearchTool supports OpenAI, Anthropic, Google, and xAI models. Could not infer a supported provider from "${provider}".

What it means

webSearchTool is a placeholder that Mastra resolves at agent-assembly time into a provider-native web-search tool. The provider must be one of OpenAI, Anthropic, Google, or xAI, inferred either directly from a string or from a model object's provider (with router-provider mapping). normalizeWebSearchProvider throws this MastraError (AGENT domain, USER category) when the inferred provider string is not in the supported set.

Source

Thrown at packages/core/src/tools/builtin/web-search.ts:41

    tool === webSearchTool ||
    (typeof tool === 'object' && tool !== null && (tool as WebSearchToolPlaceholder)[WEB_SEARCH_TOOL_MARKER] === true)
  );
}

export function normalizeWebSearchProvider(providerOrModel: unknown): WebSearchProvider {
  const provider = getProviderString(providerOrModel);
  const supportedProviders = new Set<WebSearchProvider>(['openai', 'anthropic', 'google', 'xai']);

  if (supportedProviders.has(provider as WebSearchProvider)) {
    return provider as WebSearchProvider;
  }

  const routerProvider = getRouterProvider(provider);
  if (supportedProviders.has(routerProvider as WebSearchProvider)) {
    return routerProvider as WebSearchProvider;
  }

  throw new MastraError({
    id: 'WEB_SEARCH_UNSUPPORTED_PROVIDER',
    domain: ErrorDomain.AGENT,
    category: ErrorCategory.USER,
    details: {
      provider,
    },
    text: `The built-in webSearchTool supports OpenAI, Anthropic, Google, and xAI models. Could not infer a supported provider from "${provider}".`,
  });
}

export function createWebSearchProviderTool(provider: WebSearchProvider): ProviderDefinedTool {
  const tool = getWebSearchProviderTool(provider);
  return {
    type: 'provider-defined',
    id: tool.id,
    name: tool.name,
    args: {},
  } as ProviderDefinedTool;

View on GitHub (pinned to 75dd419e61)

Solutions

1. Switch the agent's model to one from OpenAI, Anthropic, Google, or xAI when using webSearchTool.
2. If using a router/gateway, use a model string or provider object whose provider resolves to one of the four supported families (e.g. 'openai/gpt-4o').
3. For unsupported providers, remove webSearchTool and wire a provider-specific search tool manually.
4. Check the model id/provider string for typos and casing.

Example fix

// before
new Agent({ name: 'a', model: 'mistral/mistral-large', tools: { webSearch: webSearchTool } });
// after
new Agent({ name: 'a', model: 'openai/gpt-4o', tools: { webSearch: webSearchTool } });

const SUPPORTED = ['openai', 'anthropic', 'google', 'xai'];
const provider = typeof model === 'string' ? model.split('/')[0] : model?.provider;
if (!SUPPORTED.includes(String(provider))) {
  throw new Error(`webSearchTool requires one of ${SUPPORTED.join(', ')}; got "${provider}"`);
}

function isSupportedWebSearchProvider(p: unknown): p is 'openai' | 'anthropic' | 'google' | 'xai' {
  return p === 'openai' || p === 'anthropic' || p === 'google' || p === 'xai';
}

try {
  agent = new Agent({ model, tools: { webSearch: webSearchTool } });
} catch (e) {
  if (e instanceof MastraError && e.id === 'WEB_SEARCH_UNSUPPORTED_PROVIDER') {
    // fall back to a provider-agnostic search tool or log guidance
  } else throw e;
}

When it happens

Trigger: Passing webSearchTool in an agent's tools list while the configured model is from an unsupported provider (e.g. Mistral, Groq, Cohere, an openai-compatible endpoint that cannot be mapped, or a plain string model id like 'my-model' with no provider prefix).

Common situations: Developers assume webSearchTool works with any LLM provider; using a gateway/router model string whose provider maps to something outside the four supported families; typos in provider strings like 'OpenAI' or 'openai.chat'.

Related errors

• Unsupported browser provider: ${provider}
• Parallel ${operation} returned no output
• ${output.message}
• EXPERIMENT_HAS_NO_TARGET
• EXPERIMENT_ALREADY_FINALIZED

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/535ee10f4f1d4c80. Report an issue: GitHub.